Warnings and human factors expert
Expert class library · Mass tort and product liability · Either side
Evaluates whether a product's warnings and instructions were adequate and how real users notice, understand, and act on them. Draws on human factors research, ANSI Z535 warning design standards, and task and hazard analysis, and often proposes or critiques alternative warnings.
What this expert is retained to answer
- Did the existing warnings adequately communicate the specific hazard that caused the injury?
- Were the warnings placed, formatted, and worded so that users would notice and understand them?
- Would an alternative warning have given the user new information and changed the user's behavior?
- Was the hazard open and obvious to an ordinary user?
- Do the warnings comply with ANSI Z535 and industry practice, and does compliance make them adequate?
Methods
- Warning adequacy analysis
- ANSI Z535 standards review
- User perception research
- Task and hazard analysis
How the testimony is attacked
- Alternative warning never tested or grounded in research. Defendants argue a proposed alternative warning is just the expert's preference. In Hickerson v. Yamaha the Fourth Circuit affirmed exclusion of both the alternative warning and the inadequacy opinion because neither was tested or supported by research, data, or scientific theory.
- Experience alone without connecting the dots. Opponents argue the expert relies only on experience and intuition. In Jackson v. E-Z-Go the court excluded a defense human factors opinion that a rollover risk was intuitively obvious to users because it rested on anecdote and subjectivity rather than cited research.
- Literature reviews rather than primary studies. Challengers argue that relying on review articles rather than original studies is unreliable. The Jackson court admitted the opinion that different warnings would not have changed the operator's behavior, finding the cited warnings effectiveness literature reliable.
- No warnings-specific credentials. Defendants argue an engineer without warnings publications or ANSI committee membership is unqualified. In Williams v. Manitowoc the Fifth Circuit held that experience with hazard analysis, human-machine interaction, crane warnings, and industry standards was enough, and that the gaps went to weight.
- Compliance with industry standards. Manufacturers argue that warnings meeting OSHA and industry standards are adequate as a matter of law. The Fifth Circuit rejected that argument under Mississippi law and left adequacy to the jury, which had heard the warnings expert's testimony.
What the public record shows
A deliberately narrow CourtListener search, "human factors" AND warnings AND adequacy AND (Daubert OR "Rule 702"), returned 15 opinions filed since 2015, as of October 2, 2026; broader searches return more. Three that show how courts handle this class of testimony:
| Outcome | Case | Court | Why |
|---|---|---|---|
| Excluded | Hickerson v. Yamaha Motor Corp., U.S.A.882 F.3d 476 | 4th Cir. 2018 | The Fourth Circuit affirmed exclusion of the plaintiff's warnings opinions because the proposed alternative warnings were untested and the inadequacy opinion rested on no research, data, or scientific basis. |
| Limited | Jackson v. E-Z-Go Division of Textron, Inc.326 F. Supp. 3d 375 | W.D. Ky. 2018 | The court excluded the defense human factors expert's opinion that the rollover risk was intuitively obvious, because he did not connect his experience to that conclusion, but rejected the challenge to the warnings literature he relied on for other opinions. |
| Admitted | Williams v. Manitowoc Co.898 F.3d 607 | 5th Cir. 2018 | The Fifth Circuit held the district court did not abuse its discretion in qualifying the plaintiff's engineering professor as a warnings expert, treating his lack of warnings publications and ANSI committee work as matters of weight. |
Each case links to the free opinion text on CourtListener.
Under amended Rule 702
Since December 1, 2023, Rule 702 says expressly that the party offering an expert must show the court it is more likely than not that the testimony meets each requirement: that it rests on sufficient facts or data, uses reliable methods, and reflects a reliable application of those methods to the case. Questions about the basis of an opinion are no longer automatically matters of weight for the jury. For how the circuits have applied the amendment, see the Rule 702 tracker, which follows each court of appeals; for what that means for preparing or attacking this class of expert, see the guide on amended Rule 702.
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Last reviewed October 2, 2026. How this page is built: rulings are found by searching court opinions on CourtListener, and each one is read in the opinion before it is summarised here; outcomes are labelled by what the court did with the expert's testimony. No individual expert is named. This page summarises public decisions for orientation and is not legal advice; read the opinion before relying on any ruling.